1200 infection control & hospital epidemiology october 2017, vol. 38, no. 10 table 2. Incident Clostridium difficile (iCDI) Cohort Description No.


Age, median y (mean±standard deviation) Female, No. (%)


Non-white race, No. (%)


Charlson scoreb 0–2, No. (%) 3–5, No. (%) 6+, No. (%)


Community onset, community associated, No. (%)c Community onset, healthcare-facility associated, No. (%)c Hospital onset, healthcare-facility associated, No. (%)c


No. of inpatient stays in 60 d preceding iCDI 0, No. (%) 1, No. (%)


2+, No. (%)


Patient in intensive care at iCDI onset, No. (%) Any antibioticse at iCDI onset, No. (%) High-risk antibioticse at iCDI onset, No. (%) Fluoroquinolone at iCDI onset, No. (%) Low-risk antibioticsd at iCDI onset, No. (%) Intravenous vancomycin at iCDI onset, No. (%) LAPS2e at iCDI onset (mean±standard deviation) COPS2e at iCDI onset (mean±standard deviation) Admitted from skilled nursing facility, No. (%)


Recurrencea 1,455


74.0 (71.3±15.4) 831 (57.1) 351 (24.1)


1,141 (78.4) 308 (21.2) 6 (0.4)


315 (21.6) 766 (52.6) 374 (25.7)


581 (39.9) 603 (41.4) 271 (18.6) 121 (8.3) 610 (41.9) 351 (24.1) 168 (11.5) 127 (8.7) 47 (3.2)


75.0 (80.8±43.4) 58.0 (69.0±54.0) 260 (17.9)


No Recurrencea 7,223


69.0 (66.8±17.2) 4,131 (57.2) 2,068 (28.6)


5,817 (80.5) 1,394 (19.3) 12 (0.2)


2,244 (31.1) 2,804 (38.8) 2,175 (30.1)


3,953 (54.7) 2,252 (31.2) 1,018 (14.1) 853 (11.8) 3,170 (43.9) 1,764 (24.4) 687 (9.5) 835 (11.6) 166 (2.3)


76.0 (81.7±45.3) 45.0 (60.0±52.6) 843 (11.7)


Total 8,678


70.0 (67.5±17.0) 4,962 (57.2) 2,419 (27.9)


6,958 (80.2) 1,702 (19.6) 18 (0.2)


2,559 (29.5) 3,570 (41.1) 2,549 (29.4)


4,534 (52.2) 2,855 (32.9) 1,289 (14.9) 974 (11.2) 3,780 (43.6) 2,115 (24.4) 855 (9.9) 962 (11.1) 213 (2.5)


76.0 (81.6±45.0) 48.0 (61.5±52.9) 1,103 (12.7)


P Value <.0001


.9557 .0005


.0413


<.0001 <.0001 .0008


<.0001


.0005 .1682 .8090 .0175 .0017 .0361 .4591


<.0001 <.0001


NOTE. iCDI, incident Clostridium difficile infection; LAPS2, laboratory-based acute physiology score, version 2; COPS2, comorbidity point score,


version 2. aCohort consists of patients with iCDI. Patients who died during the follow-up period were removed from analysis. bSee Deyo et al24 for details on how this score was assigned. cLocus of iCDI onset is categorized as (1) community onset, healthcare-facility associated (iCDI diagnosed by a positive toxin test within 72 h


of admission or iCDI diagnosed in any outpatient setting and a hospitalization in the prior 90 d); (2) community onset, community associated (reference group in model: iCDI diagnosed by a positive toxin test within 72 h of admission or in any outpatient setting and no hospitalization in the previous 90 d); or (3) hospital onset, healthcare-facility associated (CDI diagnosed >72 h after hospital admission). These definitions were


also used by Zilberberg et al.25 dWe employed the same antibiotic classifications as Zilberberg et al.25 eFor an extended definition of LAPS2 and (COPS2), refer to the text and Escobar et al.22 For both of these scores, increasing values are associated


with increasing mortality risk. The univariate relationship of an admission LAPS2 with 30-d mortality is as follows: 0–59, 1.0%; 60–109, 5.0%, 110+, 13.7%; the univariate relationship of COPS2 with 30-d mortality is as follows: 0–39, 1.7%; 40–64, 5.2%, 65+, 9.0%.


table 3. Model Performance in the Validation Dataseta at a Predicted Risk of ≥15% Modelb,c


Age ≥65 years Basic model


Zilberberg model Enhanced model Automated model


c Statistic R2 0.546


0.591 0.591 0.587 0.605


−0.1131 −0.0910 −0.0875 −0.0924 −0.1033


0.0944 0.0937 0.0933 0.0936 0.0942


67.36 75.69 74.31 69.44 79.17


Brier Score Sensitivity Specificity PPV NPV NNE NRI IDI 11.04 92.30 9.06 ……


41.86 41.19 39.03 43.64 32.04


12.11 94.06 8.26 0.0766 0.011 11.54 93.42 8.66 0.0412 0.011 11.66 93.03 8.58 0.0387 0.014 11.09 93.49 9.02 0.0199 0.012


NOTE. c statistic, area under the receiver operator characteristic curve; R2, Nagelkerke’s pseudo-R2; PPV, positive predictive value; NPV, negative predictive value; NNE, number of incident cases one would need to evaluate to detect one recurrence; NRI, net reclassification improvement;


IDI, integrated discrimination improvement; iCDI, incident Clostridium difficile infection. aThe validation dataset consisted of 1,865 iCDI patients, of whom 144 developed rCDI. A total of 376 iCDI patients died (and thus could not be


assessed for recurrence). bSee text for description of the 4 models. “Age ≥65 years” refers to a simple decision rule based on age alone. Sensitivity, PPV, NPV, NNE, NRI,


and IDI are based on the model giving a predicted recurrence risk of ≥15% within 84 days. cWe conducted sensitivity analyses using predicted risk of ≥20%, ≥25%, and ≥30%. These results are provided in the Appendix.


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